Mazda's Straight-Six Gamble: The CX-90 Engine Nobody Expected from Hiroshima

The first time I heard about Mazda's new inline-six, I thought it was a joke.

It was 2022, and I was at a trade show in Chicago. A Mazda engineer was giving a presentation on their new large-vehicle platform, and he casually mentioned that the new CX-90 would be powered by a 3.3-litre turbocharged straight-six.

I looked at my colleague and said: "Did he just say straight-six? In a Mazda?"

He nodded. "Yeah. They're going full BMW."

I laughed. Mazda — the company that built its reputation on the rotary engine, the company that's been making four-cylinders for decades — was going to build a straight-six. In an era of downsizing, electrification, and four-cylinder hybrids. It made no sense.

And then I drove one. And I understood.

The Gambler's Logic

Mazda is a small company. They sell about 1.5 million cars a year globally — compared to Toyota's 10 million and Volkswagen's 9 million. They don't have the R&D budget to develop multiple engine families. Every decision has to be carefully calculated.

In 2015, Mazda announced their "Sustainable Zoom-Zoom 2030" strategy. The plan was to reduce CO2 emissions across their lineup by 50% by 2030, and to achieve carbon neutrality by 2050.

The obvious answer was electrification. Hybrids, plug-ins, pure EVs. That's what everyone else was doing.

Mazda took a different path. They said: "The internal combustion engine still has potential. We're going to make it cleaner, more efficient, and more engaging — and we're going to prove that it's not dead yet."

The straight-six is the flagship of that strategy. It's a statement. It's Mazda saying: "We believe in the internal combustion engine. We believe there's still life in it. And we're going to build the best one we can."

Why a Straight-Six?

The straight-six is a dying breed. BMW still builds them. Mercedes has largely abandoned them for V6s. Toyota builds a few. Jaguar used to. But for the most part, the straight-six has been replaced by V6s and four-cylinders with turbos.

Why would Mazda choose the straight-six?

1. Inherent balance. A straight-six is one of the most perfectly balanced engine configurations. The primary and secondary forces are naturally balanced, which means it's smooth, refined, and doesn't need balance shafts. It's a more elegant design than a V6.

2. Packaging. The new large-vehicle platform (which underpins the CX-90, CX-70, and the next-generation CX-5) is designed for longitudinal engine mounting. That means the engine sits north-south, with the transmission behind it. A straight-six fits perfectly in this layout — and it's easier to package than a V8.

3. Scalability. The new engine family includes both petrol and diesel variants, and it's designed to be used in rear‑drive‑biased platforms. It's also designed to work with Mazda's mild‑hybrid system (a 48‑volt starter‑generator) and plug‑in hybrid systems.

4. Emotional appeal. Mazda's brand is built on "Jinba Ittai" — the idea that the car and driver are one. A straight-six is more engaging than a turbo four. It revs more freely. It sounds better. It feels more special. And that's exactly the kind of car Mazda wants to build.

The Engine: A Technical Breakdown

Let's talk about the engine itself.

The CX-90's 3.3‑litre straight‑six (codenamed the e‑Skyactiv G) is a genuinely impressive piece of engineering. Here's what's under the bonnet:

1. Turbocharging (Twin Scroll)

The engine uses a twin‑scroll turbocharger, which means the exhaust manifold is split into two channels — one for cylinders 1, 3, and 5, and one for cylinders 2, 4, and 6. This design reduces exhaust gas interference, which means the turbo spools faster and delivers more responsive power.

The result: Maximum torque (369 lb‑ft) arrives at 2,000 RPM and holds all the way to 4,500 RPM. That's a flat torque curve that's available almost immediately.

2. Mild Hybrid (48‑Volt System)

The CX-90 has a 48‑volt mild‑hybrid system. A small electric motor (the "e‑motor") is integrated into the transmission. It provides up to 17 horsepower and 112 lb‑ft of torque to assist the engine during acceleration. It also recovers energy during deceleration.

What this means: The mild hybrid system doesn't make the car feel electric, but it smooths the transitions — the stop‑start system is seamless, the acceleration is more linear, and the fuel economy is improved by about 5‑10%.

3. Skyactiv‑X Technology

Mazda's Skyactiv‑X engine uses a "SPCCI" (Spark‑Controlled Compression Ignition) system — it's a gasoline engine that can run on compression ignition, like a diesel. The CX-90's straight‑six doesn't use the full SPCCI system (that's reserved for the smaller four‑cylinders), but it uses some of the same tech — high compression ratio, lean burn, and precise fuel injection.

What this means: The engine is efficient. Mazda claims 24 mpg combined for the CX-90, which is excellent for a 4,700‑pound SUV with 340 horsepower.

4. Low‑Friction Materials

Mazda spent a lot of time reducing internal friction. The engine uses low‑viscosity oil (0W‑20), low‑tension piston rings, and coated bearings. The result is a engine that's smooth, responsive, and efficient.

What It's Like to Drive

I've driven the CX-90 3.3T in both the standard (280 hp) and the S (340 hp) versions. Here's what I can tell you:

The engine is smooth. The straight‑six is inherently balanced, and Mazda's engineers have tuned the engine mounts and the intake system to make it almost imperceptible at idle. You can feel a slight vibration, but it's more like a gentle hum than a shake.

The power delivery is linear. The turbocharger spools quickly, and the torque comes in early and stays flat. The engine pulls cleanly from 2,000 RPM to redline. There's no sudden surge of power — it just builds smoothly and confidently.

The sound is addictive. The straight‑six has a distinctive note — a deep, resonant hum that's different from a V6's growl or a four‑cylinder's buzz. It's not as sonorous as BMW's B58, but it's close. And when you push it, it makes a sound that makes you want to push it more.

The transmission is excellent. The CX-90 uses an 8‑speed automatic that's been developed in‑house by Mazda. It's responsive, intelligent, and smooth. The shifts are quick and decisive, and the transmission always seems to be in the right gear.

The handling is balanced. The longitudinal platform and the rear‑drive bias mean that the CX-90 handles like a sports sedan, not an SUV. The front end feels light, the steering is precise, and the car rotates willingly into corners. It's not a sports car — it's too heavy for that — but it's the best‑handling three‑row SUV I've ever driven.

What I've Seen on My Lift (The Repair Reality)

The CX-90 is a new engine, and I've only worked on a handful so far. But I've already learned some things.

The Good

• The build quality is excellent. The cylinder head is well‑designed, the casting quality is high, and the tolerances are tight. This is a well‑engineered engine.

• The valve train is robust. The engine uses hydraulic lash adjusters and roller‑follower camshafts. The valvetrain is quiet and smooth.

• The turbocharger is well‑cooled. The twin‑scroll turbo has separate water and oil cooling lines, and the heat shielding is comprehensive.

• The fuel system is reliable. The direct injection system uses high‑pressure fuel injectors that are robust.

• The oil filter is accessible. The filter is on top of the engine, just like the Volvo Drive‑E. It's a five‑minute oil change.

The Unknowns

• The mild‑hybrid system. The 48‑volt system includes a battery, an inverter, and a starter‑generator. I haven't seen any failures yet, but it's a new system. The battery is under the boot floor, which is a good location (protected from heat, accessible for replacement). But the cost of a replacement battery is unknown.

• The electric water pump. The CX-90 uses an electric water pump for the battery and turbo cooling. Bosch units have a history of failing around 70,000‑80,000 miles. I'm watching this one closely.

• The PCV system. The PCV system is similar to the Volvo Drive‑E — it uses a diaphragm valve that can fail. The diaphragm is accessible, so it's likely a cheap and easy fix.

• The timing chain. The engine uses a timing chain (not a belt) that's designed to last the life of the engine. I haven't seen any failures, but the tensioner is a potential weak point.

• The turbocharger wastegate actuator. The wastegate actuator is a vacuum‑operated unit. I haven't seen any failures, but it's a potential wear item.

The early verdict: The CX-90's straight‑six is a well‑built engine. It's too early to say if it's a Toyota‑level reliable engine, but the signs are positive. I expect it to be significantly more reliable than the BMW B58 (which is already a good engine) and comparable to the Volvo Drive‑E in reliability.

The Competition: How It Stacks Up

Let's compare the CX-90's straight‑six to its competitors.

The CX-90 is the value play. It's cheaper than the BMW and Genesis, more powerful than the Volvo, and it drives better than the Genesis and the Volvo.

The BMW is the benchmark, and it's still the best‑driving SUV in the class. But the CX-90 is remarkably close — and it's $18,000 cheaper.

The Surprising Part: The Diesel

Mazda also offers a 3.3‑litre straight‑six diesel (the e‑Skyactiv D) in markets outside North America. It makes 254 horsepower and 405 lb‑ft of torque, and it's paired with the same mild‑hybrid system.

The diesel is even more efficient — Mazda claims 34 mpg combined — and it's just as smooth as the petrol engine.

The diesel isn't coming to the US (the market isn't strong enough), but it's a reminder that this engine family is designed for global use. It's not a niche engine — it's a platform that can power cars in any market.

The Long‑Term Bet

Mazda's straight‑six is a gamble. The company is investing heavily in internal combustion at a time when the industry is moving toward electrification. It's a bet that there's still a market for engaging, driver‑focused cars with internal combustion engines.

I think they're right.

The CX-90 is proof that you can build a large, heavy SUV that's genuinely fun to drive. It's proof that a straight‑six can be efficient and clean. And it's proof that Mazda hasn't lost its soul.

The CX-90 isn't a sales juggernaut. It's not going to outsell the X5 or the GLE. But it's going to win over the people who matter — the people who care about driving, who appreciate engineering, and who are willing to look past the badge.

The Family Test

I put the CX-90 through the Keller family test, just as I do with every car.

Mia's take: She loved the rear seat. The third row is actually usable, and the captain's chairs in the second row are comfortable. She said: "It's like a limousine. Can we get this one?"

Socket's take: The cargo area is 40.0 cubic feet behind the second row — larger than the Outback's, smaller than the Ascent's. Socket had room to stand and turn around, but he couldn't stretch out fully. He gave it a tail‑wag of approval — but he preferred the Ascent.

Claire's take: She drove it for a day. Her feedback: "The engine is smooth. The handling is excellent. But the ride is firm — I felt every bump on Powell. It's a sports car in SUV clothing. I like it, but I'm not sure I want to drive it every day."

My take: The CX-90 is the best‑driving three‑row SUV I've ever driven. It's not the most practical, and it's not the most luxurious, but it's the most rewarding to drive. The straight‑six is a gem — smooth, powerful, and engaging. I want one.

Mazda's straight‑six is a gamble — but it's a gamble that's paying off.

The engine is smooth, efficient, powerful, and engaging. It's the heart of a car that's genuinely fun to drive, even in an era of electrification. And it's a reminder that internal combustion still has a place in the automotive world.

If you're in the market for a three‑row SUV and you care about driving, the CX-90 is the best choice. It's cheaper than the BMW, more reliable than the Genesis (I suspect), and more powerful than the Volvo. It's a car that rewards you every time you drive it.

The CX-90 is not perfect. The infotainment system is glitchy. The ride is firm. The fuel economy is not class‑leading. But the engine — the straight‑six — is the best thing about it.

And that's saying something.